Knot slippage tester



United States Patent KNOT SLIPPAGE TESTER Camillo A. Zarroli, Lewistown, Pa., assignor to American Viscose Corporation, Philadelphia, Pa., a corporation of Delaware Application November 30, 1956, Serial No. 625,499

6 Claims. (Cl. 73-95) The present invention relates to a strand testing apparatus for determining the resistant strength of a test strand to sudden or' abrupt tensioning. In particular, the invention relates to a knot strength tester for determining the Strength of a knot which joins together two separate strands against sudden or abrupt tensioning.

With the use of yarn winding apparatus of one nature or another, the filament or strand being wound or unwound is frequently broken during the winding operation because of suddent and abrupt tensioning exerted upon the strand. The abrupt tensioning of the strand is brought about through a jerking or snapping action to which the strands or filaments are frequently subjected during the winding operation. When the filament or strand is so broken, it isnecessary for the operator to knot the broken ends together so that the winding operation may be resumed. Through careful study, it has been discovered that knots which are tied by certain operators will withstand the snapping or jerking action mentioned above while knots tied by other operators will slip or become untied because of the normal jerking or snapping action.

With the above background, it is obvious that the efficiency of the yarn winding operation will depend in part upon the strength of the knots which are formed by the operator in uniting the broken filament ends. Breakage of the filaments being wound is quite common and the efficiency of the winding apparatus and operation may be lowered considerably if the operator is a poor knot tier or if different operators of varying knot tying ability tie the knots for broken ends.

It has also been found that the holding efiiciency of a knot which unites broken ends may be of varying efliciency when used with difierent types of yarns and strands. In this respect, the holding efiiciency of the knot, of course, will depend to a great extent on the friction coefficient of the yarn. The knots in the more slippery yarns will not be as strong as those in yarns or strands which exhibit rough or slightly gripping surfaces.

To date, no satisfactory knot strength tester has been devised wherein an operator may determine the best type of knot to be used for a specific type filament or strand or the amount of pull that should be exerted in tying together the broken ends. Such a knot tester would be most desirable for instructing the operators as to the knot strength necessary, as well as the type of knot desired in respect to different type yarns.

It is therefore one object of my invention to provide a strand strength tester for accurately and efliciently determining the resistant strength of a strand to abrupt and sudden tensioning.

A further object of my invention is to provide a novel and improved knot strength tester for determining the strength of a knot which is formed to unite separate strands or filaments into a single unit.

Other objects and advantages of my invention will become more apparent from a study of the following description and drawing in which:

2,881,615 Patented Apr. 14, 1959 Figure 1 is a front view, partly sectioned, of my strand strength tester; and

Figure 2 is a side view, partly sectioned, of the strand tester shown in Figure 1.

Briefly, my knot tester comprises a base or stand having a pair of spaced-apart vertical supports. The test strand is secured to one of the supports and is laced over a rotatable guide such as a pulley which is afiixed to the second support. The opposite end of the test strand is secured to a weight. A hoisting lever is pivotally mounted to the second support and has secured thereto a hoist strand which is also secured at its opposite end to the weight. A cam arrangement periodically raises the hoisting lever which raises the weight by virtue of the hoist strand a certain distance after which the cam releases the lever, thus permitting the weight to fall freely. As the weight reaches its lowermost position, the test strand is jerked or snapped. If the strand does not break, the cam again raises the hoisting lever and the operation is repeated. Counting means are provided for recording the number of free falls of the weight. Should the test strand break, the weight drops upon a pair of electrical contacts which set up signals through a relay system to interrupt or terminate the operation of the cam which controls the hoist lever movement.

The jerk or snap to which the knotted filament or strand is subjected is equal to a force consisting of the weight of the plumb-bob weight times the distance through which it falls. This snapping force can be adjusted when required by merely using diiferent weight plumb-bobs or changing the fall distance of the plumbbob or both.

Referring now to the drawing, a vertical support 1 is secured to a base or table 3. Strand anchoring means, preferably in the form of a hook 5, is afiixed to the top portion of the vertical support 1. A second vertical support 7 is also afiixed to the base 3 and has a rotatable guide member 9, preferably a pulley, rotatably and freely mounted to the upper end of the vertical support 7. As seen in the drawing, the support 7 is curved so that the upper end of the support and the pulley are in substantial alignment with the vertical support 1.

Secured to the upper portion of the vertical support 7 is a pivotally mounted hoisting lever 11. One end of the lever has a strand retaining hook 13 to which one end of a hoisting strand 15 is secured. The hoisting strand is threaded through an eyelet guide 17 ailixed to the lowermost end of a downwardly extending arm 19 initiating from the uppermost end of the curved or second vertical support 7. The opposite end of the hoisting strand 15 is secured to a weight 21, preferably a plumb-bob.

To hoist the weight 21 with the lever 11, a rotatable cam is provided, preferably in the form of an arm 23 and is mounted on a third vertical support 24 also aifixed to the base 3. The arm 23 is mounted upon one end of shaft 25 supported in bearing assembly 25. A drive pulley 26 is supported on the opposite end of the shaft. A lower driven pulley 26' mounted upon shaft 27 of a small fractional H.P. motor 28 drives the upper pulley 26 through drive chain or belt B to rotate shaft 25 and the arm 23 supported thereby. When the motor is in operation, the arm 23 will rotate continuously, preferably from 10 to 30 r.p.n1., in a counter-clockwise direction as indicated by the arrow of Figure 2. As will be explained more fully hereinafter, the arm 23 operates to raise the hoisting lever 11 during each cycle of arm rotation.

A predeterrnining counting mechanism 29 operated by the drive pulley 26 through shaft 29 records each complete revolution of the arm 23 and terminates the operation after a specified number of revolutions of the arm 23. The counter is connected by a suitable electrical circult to the motor 28 to stop operation of the motor upon completion of the predetermined revolutions of the arm 23.

In operation, the strand test sample 40 is secured at its one end to the anchoring hook 5, laced over the pulley 9, and secured at its opposite end to the weight 21. As seen in Figure 1 of the drawing, the test strand 40, in this case, comprises two separate ends of yarn or strands which are secured together by a knot 42. In this instance therefore, the resistant strength of the knot '42 to sudden and abrupt tensioning is to be tested or determined. It should be pointed out, however, that the strength of a continuous, non-broken filament or strand may be also tested with respect to the effect of sudden and abrupt tensioning exerted thereupon.

After the test strand 40 has been laced up, the motor 28 is put into operation whereby the lower pulley 26' aflixed to the motor shaft 27 rotates the upper pulley 26 through the drive belt B. The shaft for the upper pulley and arm 23 are rotated in a counter-clockwise direction whereby the arm 23 rotates in a continuous cycle. As the arm 23 moves downwardly from the 12 oclock position toward the 9 oclock position, it contacts the butt end of the hoisting lever 11 to depress the end of the lever and raise the opposite end of the lever 11 and the weight 21 connected therewith through the hosting strand 15. As the arm 23 approaches the 8 oclock position, .it moves out of contact with the butt end of the hoisting lever 11 whereupon the lever and weight 21 will fall freely. When the weight 21 reaches its lowermost position, it exerts a jerking or snapping action upon the test sample 40. As seen in Figure 2 of the drawing, the hoisting strand 15 is in a relaxed non-tensioned state when the weight 21 is in its lowermost position. The hoisting strand 15 will not therefore interfere in any manner with the free fall of the weight 21. During one cycle of the arm 23, the shaft 29 will rotate the counting mechanism and record the completion of one cycle of the arm. If the knot of test strand does not slip because of the snapping or jerking action exerted upon it, the arm 23 will continue to rotate to repeat the above cycle just described.

Should the jerking or snapping action exerted upon the sample 40 be excessive for the knot 42 holding the ends of the sample 40 together, the knot will slip since this is the weakest point of the sample 40 and the weight 21 will drop upon electrical contacts 50, to set up a signal through a relay system, not shown, to interrupt and termimate the operation of motor 28. This action will, of course, terminate the rotation of the cam arm 23.

As seen in the drawing, a vertically extending housing is mounted on base 3. The housing is open at the top to receive the weight 21. With this arrangement, the path of-the falling weight 21 is confined Within the housing. The housing 55 also supports the cut-oil electrical contacts 50, 50.

I have disclosed herein a strand testing apparatus which operates in a highly satisfactory manner to determine the resistant strength of a knot used to unite two separate orbroken ends of a yarn or other strand to sudden and abrupt tension. As mentioned above, such an apparatus is highly desirable for determining the best type of knot to be used with various types of yarns and to determine the pull to be exerted by various operators when forming the knot.

While preferred embodiments of the invention have been shown and described, it is not intended that the invention be limited thereto and modification may be made within the scope of the appended claims.

I claim:

1. A strand tester for determining the resistance of a strand to abrupt tensioning comprising a support, a strand anchoring means afiixed to the support to which one end of the strand is secured, a weight to which the opposite end of the strand is secured, means for raising the weight to a free fall position, and a flexible support connecting the Weight raising means with the Weight, said flexible support being in a relaxed non-tensioned state when the weight is at its lowermost free fall position as determined by the length of the strand secured to the weight.

2. A knot strength tester for testing the resistance of a knot which unites two separate strands to sudden and abrupt tensioning comprising a base, a first vertical sup port affixed to the base, strand anchoring means afiixed to said support to which one end of the knotted test strand is secured, a second vertical support afiixe-cl to the base, a guide affixed to the second vertical support over which the test strand is passed, a lever pivotally and freely mounted on said second support, a hoisting strand secured at one end to one end of said lever, a weight to which is secured the opposite end of the test strand, the opposite end of said hoisting strand also being secured to said weight, lever raising means secured to the base for periodically raising the lever a specified distance and releasing the lever so that the weight will fall freely, and means for driving the lever raising means.

3. A knot strength tester according to claim 2 wherein the lever raising means comprises a driven rotatable cam.

4. A 'knot strength tester according to claim 3 comprising cut ofi signals for the driving means for the lever raising means 'aflixed to the base at a point in alignment with and below the lowermost position of the weight.

5. A knot strength tester according to claim 4 wherein the cut off signals are supported in opposed manner in a vertically disposed housing which is open at the top and through which the weight falls.

6. A knot strength tester according to claim 2 comprising a counting mechanism which is operated by the driving means for the lever raising means.

References Cited in the file of this patent UNITED STATES PATENTS 1,414,427 Lynch May 2, 1922 1,604,141 Amsler Oct. .26, 1926 1,785,690 Buflum Dec. 16, 1930 2,612,040 Rhodes Sept. 30, 1952 2,660,880 Vivian Dec. 1., 1953 FOREIGN PATENTS 572,749 Germany Mar. 22, 1933 

